Acoustic chamber



July 7, 1931. J, c, KARNES 1,812,879

ACOUSTIC CHAMBER Filed Nov. 21, 1329 Q flames llKarne By M fl flwj A TTORNEY.

Patented July 7, 1931 JAMES C. KARNES, OF BUFFALO, NEW YORK ACOUSTIC CHAMBER Application filed November 21, 1929. Serial No. 408,841.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRIL 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government of governmental purposes, without the payment to me of any royalty thereon.

This invention relates to an acoustic chamber.

An essential component of an anti-aircraft defense system consists of a corps of observers whose duty is to ascertain and report the lolo cation and number and type of hostile aircraft, the angle of approach, and the altitude. This is a most difficult assignment, especially in the dark, and requires considerable and continuous practice to secure proficiency. At

the present time such practice is conducted outdoors and requires that planes be sent aloft to provide a movable sound source.

Because of the fine distinctions which must be made by aural detection and comparison it is impossible to conduct the practices indoors with moving pictures and sound records because an auditorium suited to the purpose must have perfect acoustic properties.

In providing sound accompaniment for '25 motion pictures, the number and position of the sound reproducers is controlled by the acoustic properties of the auditorium. The general practice is to distribute the horns about the stage but in any case, the arrangement is a compromise between clear and natural reception over the maximum area of the auditorium and synchronization of the sound and picture.

In order to insure excellent acoustic properties in an auditorium and practically perfect synchronization at all points therein it is proposed in the present invention to provide a ceiling in the form of an immense horn, preferably having an exponential variation of cross section with the length and the axis of the horn being perpendicular to the inclined floor.

With the foregoing and other objects in view, the invention resides in the novel arrangement and combination of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention.

A practical embodiment of the invention is illustrated in the accompanying drawings, wherein Fig. 1 is a schematic view in central longitudinal elevation of an auditorium con structed in accordance with the invention;

ig. 2 is a :iioor plan thereof;

clin

ed in accordance with standard practice to provide for tiers of seats 8.

In the preferred form of the invention shown in Fig. 1 the ceiling 9 is in the shape of an immense conical horn whose axis is perpendicular to the floor so that the distance from the throat or apex 10 of the horn to all of the seats is practically the same.

side

The

s of the horn are convex in the direction of their length and preferably the horn is ofe xponential cross section, the form of the equation used in determining the design being A=A0e in which A is the cross sectional area at any point; A0 is the cross sectional area at the small end; 6 is the i aperian base; m is a constant determining the rate of flare; m is the distance of A along the axis measured from the small end.

he ceiling at the mouth of the horn meets the side walls 11 at a convenient height above the floor and as occasion may require, the

latter are to be covered with drapes.

In F 1g. 2 the floor 7 1s circular in shape, being a pro1ect1on of the mouth of the horn.

Int

his form sound emanating from the apex 10 of the horn will be received by the entire aud the the app ience at practically the same time and synchronization between the sound and picture will, consequently, be uniformly licable throughout the auditorium.

ound reproducers 12 may be placed at the of their length, that is, in the direction of 1 height of the auditorium. The forward wall 13 is extended to a point well to the rear of the auditorium so that it is of considerably greater length than the rear wall 14. The

side walls, 15-15 are uniform. In this instance the axis of the horn formed by the ceiling will not be perpendicular to the floor and the sound emanating from the apex 16 Will be required to travel unequal distances to the various points of the audience but such inequality will not be nearly as disproportinate as now obtains when the sound is emanated from the stage. In modifying some auditoriums it will be found impracticable to alter certain sides; for example, the rear side containing the balcony and, accordingly, such rear side may remain vertical.

In an auditorium formed in accordance with the present invention the reception of both vocal and instrumental sounds will be clear and natural. The resonance will be of short duration and constant throughout all parts and the positioning of the audience 7 when in a plane perpendicular to the axis of the horn and substantially parallel to the sound Waves will provide an effective absorbent which will insure againstreverberation.

I claim:

1. In an acoustic chamber, a ceiling formed in the shape of a horn having an exponential variation of cross section with the length and a floor in projection of the mouth of the horn, the axis of the horn being perpendicular to the floor.

' 2. In an acoustic chamber, a ceiling formed in the shape of a horn having an exponential variation of cross section with the length and a floor in projection of the mouth of the horn.

3. In an acoustic chamber,'a ceiling formed in the shape of a horn having an exponential variation of cross section with the length.

In an acoustic chamber, a ceiling formed in the shape of a horn having an exponential variation of cross section with the length and a sound reproducer horn in prolongation of the horn constituted by the ceiling. V

5. In an acoustic chamber, a ceiling formed in the shape of a horn and a sound reproducer horn in prolongation of the horn constituted by the ceiling.

6. In an acoustic chamber, a ceiling formed 

